Progress in application of cyclic single-stranded nucleic acids.

Cyclic nucleic acids are biologically stable against nucleic acid exonucleases due to the absence of 5' and 3' termini. Studies of cyclic nucleic acids mainly focus on cyclic single-stranded nucleic acids. Cyclic single-stranded nucleic acids are further divided into circular RNA (circRNA) and circular single-stranded DNA (cssDNA). The synthesis methods of circRNA include lasso-driven cyclization, intron-paired cyclization, intron cyclization, intron complementary pairing-driven cyclization, RNA-binding protein-driven cyclization, and artificial synthesis depending on the source. Its main role is to participate in gene expression and the treatment of some diseases. Circular single-stranded DNA is mainly synthesized by chemical ligation, template-directed enzyme ligation, and new techniques for the efficient preparation of DNA single loops and topologies based on CircLigase. It is mainly used in rolling circle amplification (RCA) technology and in the bioprotection of circular aptamers and second messengers. This review focuses on the types, synthesis methods, and applications of cyclic single-stranded nucleic acids, providing a reference for further research on cyclic single-stranded nucleic acids.

[Modified Biochar for Remediation of Soil Contaminated with Arsenic and Cadmium: A Review].

Binary pollution of arsenic (As) and cadmium (Cd) has become the main soil environmental problem in China. As an adsorbent or immobilizer, modified biochar is playing an increasing role in the remediation of As and Cd-contaminated soil. Here, the limitations regarding the primitive biochar as an immobilizer for the remediation of As and Cd-contaminated soil were highlighted by this study. Meanwhile, the biochar modification methods for the remediation of As and Cd-contaminated soil were reviewed, and the main interaction mechanisms were analyzed. Finally, the prospects and questions for the future remediation of soil contaminated with As and Cd using modified biochar were proposed. The results showed that metal-modified biochar had a better synergistic effect on the remediation of As and Cd-contaminated soil and thus had better application prospects. The immobilization mechanisms of As and Cd using biochar material remediation were affected by its modification methods. For example, the mechanisms for (non)metal-modified biochar involved the functional group-induced bonding complexation, co-precipitation, and oxyanion As redox; for microorganism-modified biochar, the mechanisms were precipitation and As redox, and those for physical- and acid-modified biochar only included the physical adsorption and weak electrostatic attraction. In view of the limitations of present research on the application of modified biochar for the remediation of As and Cd-contaminated soil, future research is suggested to study the following:① the effect of biomass feedstock type, pyrolysis temperature, preparation conditions, cost, and soil aging; ② evaluation for stability and durability of heavy metal immobilization by modified biochar remediation under different environmental factors; and ③ insight to key remediation mechanisms of As and Cd-contaminated soil by material.

Correlation between Duffy blood group phenotype and breast cancer incidence.

BACKGROUND: Different ethnicities have different distribution of Duffy blood group (DBG) phenotypes and different breast cancer morbidity. A study in our lab demonstrated that Duffy antigen/receptor for chemokines (DARC, also known as DBGP, the Duffy protein phenotype), led to the inhibition of tumorigenesis. Therefore, we tested the hypothesis that DBGP is correlated with breast cancer occurrence. METHODS: DBGP proteins were examined by indirect antiglobulin testing with anti-FYa and anti-FYb antibodies. The phenotypes were classified into four groups according to the agglutination reactions: FYa + FYb+, FYa + FYb-, FYa-FYb + and FYa-FYb-. The phenotypes and pathological diagnosis of consecutively hospitalized female patients (n = 5,022) suffering from breast cancer at the Shanghai Cancer Hospital and Henan Province Cancer Hospital were investigated. The relationships between DBGP expression with breast cancer occurrence, axillary lymph status, histological subtype, tumor size pathological grade and overall survival were analyzed. RESULTS: The incidence of breast cancer was significantly different between FYa + FYb + (29.8%), FYa + FYb- (33.2%), FYa-FYb + (45.6%) and FYa-FYb- (59.1%; P = 0.001). Significant different numbers of breast cancer patients had metastases to the axillary lymph nodes in the FYa + FYb + group (25.1%), FYa + FYb- (36.9%), FYa-FYb + (41.0%) and FYa-FYb- (50.0%, (P = 0.005). There was a statistical significance (p = 0.022) of the overall survival difference between patients with difference phenotypes. No significant difference was observed in cancer size (t-test, p > 0.05), histological cancer type (Fisher's exact test, p > 0.05) or histological grade (Fisher's exact test, p > 0.05) between every each DBGP group. CONCLUSIONS: DBGP is correlated with breast cancer incidence and axillary lymph node metastasis and overall survival. Further investigations are required to determine the underlying mechanism of Duffy blood group phenotype on breast cancer risk.

Rapid separation and identification of anthocyanins from flowers of Viola yedoensis and V. prionantha by high-performance liquid chromatography-photodiode array detection-electrospray ionisation mass spectrometry.

INTRODUCTION: Anthocyanins are important plant secondary metabolites. They show strong antioxidant activities and have potential as anti-cancer agents. Viola yedoensis and V. prionantha are traditional Chinese medicines and ornamental plants. However, the anthocyanin compositions of these two species are still unresolved. OBJECTIVE: To develop a rapid and reliable high-performance liquid chromatography (HPLC) method for the separation and identification of anthocyanins from V. yedoensis and V. prionantha. METHODOLOGY: Samples were extracted in methanol-water-formic acid-TFA (70:27:2:1, v/v). HPLC analysis was done on a C(18) column (TSK-GEL ODS-80Ts: 150 × 4.6 mm i.d.). Four solvent systems were tested to optimise the separation of anthocyanins using different gradient separation systems. HPLC-photodiode array detection (DAD) coupled to electrospray ionisation mass spectrometry (ESI-MS) was used to carry out the comprehensive characterisation of anthocyanins. RESULTS: Fourteen anthocyanins were characterised within 40 min with satisfactory peak resolution by a gradient composed of 10% aqueous formic acid and formic acid-acetonitrile-water (10:40:50, v/v). The calibration curve showed an excellent linear regression (r(2) = 0.9995) and low intra- and inter-day variations (RSD < 3.67%). The detected anthocyanins derived from Dp, Cy, Pt, Mv and Pn, could be divided into three groups: non-acylated glycosides, acetylglycosides and coumaroylglycosides. Anthocyanins distribution exhibited remarkable differences in aglycone levels and acylation patterns. CONCLUSION: The optimised method was successfully applied for the analysis of 14 anthocyanins from V. yedoensis and V. prionantha. The identification of anthocyanin constitutions is valuable for breeding and will open up new prospects for their medicinal application.

[Effects of Earthworms/Biochar on Bacterial Diversity and Community in As-contaminated Red Soil].

Cerium-manganese modified biochar (MBC) combined with earthworms (Eisenia foetida) can immobilize arsenic (As) in red soils. In this study, high-throughput sequencing technology was used to explore the combined effects of MBC and E. foetida on bacterial diversity and community structure in As-contaminated red soils. The results showed that the single earthworm treatment had the highest diversity index, whereas the diversity index decreased in the single biochar or MBC treatment, indicating that earthworms can boost the growth of bacteria in the soil, and the addition of biochar/MBC all decreased the bacterial diversity of soils. When biochar/MBC was combined with earthworms, the diversity index increased to some degree. In terms of bacterial community structure, the relative abundance of Proteobacteria and Bacteroidetes increased significantly in each treatment, especially for MBC-earthworm treated soil, in which the relative abundance was increased by 17.08% and 329.47% for Proteobacteria and Bacteroidetes, respectively, compared to that in the control (CK). Otherwise, those abundances were decreased by 19.18% and 48.76%, respectively, for Acidobacteria and Chloroflexi. Correlation analysis results showed that the soil water-soluble As (WSAs) was negatively correlated with the relative abundances of Proteobacteria and Bacteroides (P<0.05) but was positively correlated with Acidobacteria and Chloroflexi (P<0.05), which indicated that with the decrease in WSAs in soils, the bacteria of Proteobacteria and Bacteroides reproduced rapidly, whereas the Acidobacteria and Chloroflexi were inhibited. Moreover, different treatments induced selective changes in the bacterial community, in which earthworms significantly promoted the proliferation of γ-Proteobacteria, Flavobacteriales, Aeromonadales, and Variovorax and earthworms improved the immobilization effect of As by promoting the growth of these bacteria.

[Predictive value of (99)Tc(m)-MIBI scintimammography in evaluation of the efficacy of neoadjuvant chemotherapy in patients with operable breast cancer].

OBJECTIVE: To investigate the value of technetium-99m methoxyisobutylisonitrile ((99)Tc(m)-MIBI) imaging in predicting the efficacy of neoadjuvant chemotherapy (NCT) and prognosis in patients with operable breast cancer. METHODS: Sixty five patients with breast cancer underwent (99)Tc(m)-MIBI scintimammography before NCT, and static planar images were taken at 10 min and 180 min after scintimammography. The clearance rate was calculated in each patient, correlation between the clearance rate and efficacy of NCT, and the disease free survival rate were analyzed. RESULTS: The mean clearance rate of 65 patients was (17.4 ± 6.8)%. The efficacy of NCT was 86.2% (CR 4 cases, PR 52 cases, SD 8 cases, and PD 1 case), and the mean clearance rate of patients with good response or poor response of chemotherapy were (15.5 ± 5.0)% and (29.2 ± 3.2)%, respectively. There was a significant difference between the two groups. The average disease free survival rate in the group with low clearance rate was (75.8%, P = 0.046), significantly higher than that in the group with high clearance rate (53.1%). CONCLUSION: Scintimammography of (99)Tc(m)-MIBI may be used to evaluate the efficacy and prognosis of NCT for patients with operable breast cancer.

[Predicative value of 99mTc-MIBI scintimammography in neoadjuvant chemotherapeutic effect of patients with operable breast cancer].

OBJECTIVE: To evaluate the relationship between the clearance rate of technetium-99m methoxyisobutylisonitrile ((99m)Tc-MIBI) in scintimammography and the efficacy of neoadjuvant chemotherapy (NCT) of patients with operable breast cancer. METHODS: Seventy-eight patients with breast cancer underwent (99m)Tc-MIBI scintimammography at pre-NCT. And static planar images were taken at 10 min and 180 min post-scintimammography. The clearance rate was calculated in each patient. And the efficacy of NCT was evaluated after 2 cycles. RESULTS: The clearance rates of patients with a poor or good efficacy of chemotherapy were 24.21% ± 6.38% (n = 14) and 14.13% ± 5.98% (n = 64) respectively. There was significant difference between two groups. And a significant correlation was observed between the efficacy of chemotherapy and the clearance rate of (99m)Tc-MIBI (r = -0.539, P < 0.001). CONCLUSION: The scintimammography of (99m)Tc-MIBI may be employed to evaluate the efficacy of NCT.

Integrated gene expression profile predicts prognosis of breast cancer patients.

Gene expression data has in recent years demonstrated the superior capacity to predict the prognosis of breast cancer patients unreceiving adjuvant chemotherapy comparing to the information available from traditional clinical and pathological sources. Meanwhile, adjuvant chemotherapy can significantly improve survival of breast cancer. It would be inappropriate to ignore its effect on prognosis. We hypothesized that an integrated gene expression profile can predict the prognosis of breast cancer patients receiving chemotherapy. Therefore, we screened the specific gene markers and constructed an integrated 24-gene signature by low-density microarray including the "poor signature" and genes related to resistance to chemotherapy. The gene signature stratified correctly patients into good prognosis group and poor prognosis group. In addition, the Kaplan-Meier analyses for disease-free survival as a function of the 24-gene signature showed highly significant differences between the two groups (Log Rank test P < 0.0001 = Univariate and multivariate Cox's proportional-hazards regression analyses indicated that the signature represents the strongest independent prognostic factor for breast cancer patients. When compared with single signature, such as Oncotype DX and 70 poor signature, the integrated signature showed more predominant power of predication in breast cancer patients receiving chemotherapy. Such integrated signature will critically aid clinical decision making at the level of individualization for most breast cancer patients receiving chemotherapy.

[Cerium-manganese Modified Biochar Immobilizes Arsenic in Farmland Soils].

Loaded cerium and manganese modified biochar (MBC) was prepared by high temperature pyrolysis at 600℃, and three kinds of arsenic (As) contaminated soils were selected for remediation, including red soil, yellow soil, and purple soil with different basic properties. During the soil incubation experiment, the goal of this research was to investigate the influence of MBC as a stabilizer of the mobility of arsenic in these three soils after treated by biochar (BC) and MBC. The results revealed that the application of MBC resulted in a significant decrease of water soluble arsenic content in the three different kinds of soils. With the additional amount increasing, the stabilization efficiency of soil arsenic increased continuously. When the applied amount of MBC ranged from 1% to 10%, the stabilization efficiency of arsenic was in the range of 70%-99%. The corresponding stabilizing efficiencies of the red, yellow, and purple soils were 70.59%-94.72%, 75.24%-98.35%, and 76.53%-99.61%, respectively, after being treated by MBC at 1%-10%. At a higher addition of 10% MBC, the efficiency of stabilization reached 95%. On the contrary, the addition of unmodified biochar caused the activation and dissipation of As in soils. Comparatively speaking, according to the stabilization efficiency, the three soils ranked in this decreasing order:purple soil > yellow soil > red soil. It also illustrated that the addition of MBC into soils led to the conversion of active arsenic to stable ones in soil, indicating the conversion from non-specifically sorbed (F1) and specifically sorbed (F2) to well-crystallized hydrous oxides of Fe and Al (F4) and residual phases (F5), which reduced the mobility of arsenic in these soils. According to the analysis of scanning electron microscopy (SEM) and X-ray diffraction analysis, the immobilization of arsenic by MBC was strongly related to the successful loading of cerium-manganese oxide onto biochar. Therefore, MBC can be used to make suitable amendments to immobilize As in soils for remediation of arsenic-contaminated farmland soils.

[Accumulation Characteristics of Heavy Metals in Greenhouse Soil and Vegetables in Siping City, Jilin Province].

Based on the typical greenhouse vegetable production system in Siping City, Jilin Province, 124 soil samples were collected from greenhouse soils growing vegetables (GSGV), fields growing maize (FGM), and forest soil (FS) under different land utilization patterns. In addition, other samples including greenhouse vegetables (81), fertilizers (50), and irrigation water (10) were also collected in the studied region. To illustrate the accumulation characteristics of heavy metals in GSGV and greenhouse vegetables, the heavy metal content of different samples was measured using inductively coupled plasma mass spectrometry (ICP-MS) technology. The results indicated that the heavy metal content in GSGV was much higher than that in FGM and FS except for lead (Pb). Heavy metals including cadmium (Cd), copper (Cu), chromium (Cr), nickel (Ni), and zinc (Zn) in GSGV presented with various degrees of accumulation. The mean value of Cd content in the soils in the investigation region was 0.45 mg·kg-1, with about 42.8% of all the soil samples exceeding the Cd content criterion of the Environmental Quality Evaluation Standard for Farmland in Greenhouse Vegetable Production (HJ 333-2006). The content of the other heavy metals was in the normal range, and all met the regulations of the standard. In comparison with different vegetable categories, leafy vegetables showed much higher heavy metal concentrations (Cd 0.033 mg·kg-1 fresh weight) than did fruity ones. In total, about 2.5% and 1.2% of vegetable samples exceeded the regulated values of Cd and Pb recommended by the Standard of Food limits, respectively. With the cultivation time prolonged, heavy metal concentration in soils and vegetables all increased synchronously as the pH value decreased. The content of heavy metals in greenhouse vegetables was significantly influenced by soil pH and organic matter. It can be concluded that the health risk of greenhouse vegetables increased with GSGV accumulating more heavy metals due to the substantial application of chemical fertilizer and manure containing high level of heavy metals.

Isolation of a human gallbladder cancer cell clone with high invasive phenotype in vitro and metastatic potential in orthotopic model and inhibition of its invasiveness by heparanase antisense oligodeoxynucleotides.

The mechanisms involved in gallbladder cancer metastasis still remain unclear to date. The poor understanding is due, in part, to the lack of ideal cell line and animal model for study. In the present study, 21 cell clones were isolated from the human gallbladder carcinoma cells GBC-SD and the cell clone GBC-SDH(i) with high invasive phenotype was fished out. The invasive phenotype and metastatic potential of GBC-SDH(i) were confirmed in a novel surgical orthotopic implantation model of gallbladder cancer in nude mice. Heparanase, an endoglycosidase that degrades heparan sulfate, is a critical mediator of tumor metastasis and angiogenesis. RT-PCR, real time RT-PCR and western blot showed that the expression levels of heparanase were significant difference between GBC-SDH(i) and its parent cells. After treated with antisense oligodeoxynucleotides, the heparanase mRNA and protein expression in GBC-SDH(i) cells were significantly decreased and its invasive potential in vitro was inhibited in a dose-dependent manner. The study provides a useful cell clone and a clinically relevant orthotopic tumor model for the metastatic study in human gallbladder cancer. The roles of heparanase in gallbladder cancer are also evaluated.

[The relationship between 99mTc-MIBI scintimammography of breast cancer and multidrug-resistant proteins].

OBJECTIVE: To evaluate the relationship between the clearance rate of technetium-99m methoxyisobutylisonitrile ((99m)Tc-MIBI) in scintimammography and multidrug-resistant proteins expression in breast cancer tissues. METHODS: Seventy-six patients with breast cancer underwent (99m)Tc-MIBI scintimammography before treatment, and static planar images were taken at 10 min and 180 min after scintimammography. The clearance rate of (99m)Tc-MIBI was calculated in each patient. Immunohistochemical analysis was performed on pathological specimens of the 76 breast tumors to determine the expression of P-glycoprotein (P-gp), glutathione S-transferase Pi (GST-pi) and topoisomerase II (Topo II). RESULTS: The clearance rate was significantly higher in 36 patients with positive P-gp expression when compared with that in 40 patients with negative P-gp expression. There was no significant relationship between GST-pi, Topo II and the clearance rate of (99m)Tc-MIBI. CONCLUSION: The clearance rate of (99m)Tc-MIBI in breast imaging may be used to evaluate the P-gp level in breast cancers.

Assessment on the pollution of nitrogen and phosphorus of Beijing surface water based on GIS system and multivariate statistical approaches.

This paper presented the characteristics of nitrogen and phosphorus pollution in Beijing surface water during the survey. A significant difference was found out in concentration distribution of various parameters of nitrogen and phosphorus. Most water bodies in five water systems were polluted by total nitrogen with the content even up to 120 mg/L which was higher than exceeded the fifth class standard of national surface water quality standard GB3838-2002 except for several segments of Chaobaihe and Yongdinghe. Ammonia and phosphorus showed a similar tendency of distribution with higher content in Daqinghe, Beiyunhe and Jiyunhe water systems, but with relatively low concentrations in Chaobaihe and Yongdinghe water systems. Meanwhile, nitrate was found at comparatively low content (mostly less than 10 mg/L) and could fit for corresponding water quality requirements. Totally, the water quality of Daqinghe, Jiyunhe and Beiyunhe river systems as well as the lower reaches of Yongdinghe and Chaobaihe was contaminated seriously with high content of total nitrogen and phosphorus. Through multivariate statistical approaches, it can be concluded that total nitrogen, ammonia and total phosphorus was highly correlated to chemical oxygen demand, biochemical oxygen demand, dissolved oxygen and electrical conductivity, which explained the same pollution source from anthropogenic activities.

Clomazone dissipation, adsorption and translocation in four paddy topsoils.

Laboratory experiments about the dissipation, adsorption and translocation in four paddy topsoils were conducted in this paper. From the results it can be concluded as follows: the dissipation rate of clomazone differed greatly in different paddy soil derived from different parent materials. The half-lives for clomazone degradation in paddy soils ranged from 5.7 to 22.0 d. The order of clomazone dissipation rate was reddish yellow paddy soil > alluvial sandy paddy soil > yellow clayey paddy soil > purple sandy paddy soil. Clomazone sorption quantity was significantly correlated with organic carbon (R2 = 0.62) and clay content(R2 = 0.67) in the tested paddy soils. Positive correlation was found between apparent Kd value and cation exchange content(CEC). The consequences for the adsorption of different soils were purple sandy paddy soil > yellow clayey paddy soil > reddish yellow paddy soil > alluvial sandy paddy soil. Under the simulated rainfall of 200 mm through four different unsaturated soil lysimeters over 24 h, clomazone was readily to be leached into lower surface soil and there was about 2.6%--4.2% of applied clomazone leached out of 20 cm cultivated soil layer. Translocation experiments showed that the order of clomazone leaching ability was: alluvial sandy paddy soil > reddish yellow paddy soil > yellow clayey paddy soil > purple sandy paddy soil. Simple regression results manifested that factors like CEC, organic carbon, clay, and adsorption rate constant had been negatively correlated with the percentage of clomazone loss from soil lysimeters.

[Effects of different fertilization regimes on abundance and community structure of the nirK-type denitrifying bacteria in greenhouse vegetable soils].

The community structure and abundance of nirK-type denitrifying bacteria in different soil layers (0-20 cm and 20-40 cm) under various fertilization regimes in Wuwei, Gansu Province were investigated by the combination of terminal restriction fragment length polymorphism (T-RFLP) and real-time quantitative PCR. Results showed that the nirK-type denitrifying bacteria community structure was significantly affected by fertilization regimes, especially for 70, 156 and 190 bp T-RFs that represented the dominant populations in greenhouse soil. Fertilization regimes significantly influenced the abundance of nirK gene in the 0-20 cm soil layer with the highest abundance of nirK gene copy number (2.16 x 10(7) copies x g(-1) soil) detected in the manure treatment (M), which was 2.04 and 2.02 times of that in the control (CK) and chemical fertilizer (NPK) treatments, respectively. Both the dominant population and abundance of nirK-type denitrifying bacteria in the greenhouse soil were significantly different between the 0-20 cm and 20-40 cm soil layers, and the nirK-type denitrifying bacteria community structure and abundance in the greenhouse soil were obviously different from that in the field. Soil pH, soil organic matter content and nitrate-N content had the greatest influence on the bacterial community composition. Phylogenetic analysis indicated that there were not only anaerobic nirK-type denitrifying bacteria in greenhouse soil, but also aerobic denitrifying bacteria, such as Rhizobium, Ochrobactrum, Agrobacterium.

[Effects of vegetable cultivation years on microbial biodiversity and abundance of nitrogen cycling in greenhouse soils].

The effects of facility vegetable cultivation years (three, nine, fourteen or seventeen years) on biodiversity and abundance of soil microorganisms, such as bacteria, ammonia oxidizing bacteria (AOB) and nirK type denitrifying bacteria, in the greenhouse soils in Wuwei of Gansu Province, China were determined by the combined analyses of terminal restriction fragment length polymorphism (T-RFLP) and real-time quantitative PCR. The results showed that the dominant population structure and abundance of bacteria, AOB, nirK type denitrifying bacteria in the soils were significantly different from those in the farmland fields. The dominant population also changed with the cultivation years. With the increase of vegetable cultivation years, the abundance of 16S rRNA and nirK gene in the 0-20 cm soil layer first increased and then decreased, with the maximum values of 9.67 x 10(9) and 2.30 x 10(7) copies x g(-1) soil at year 14 and year 9, being as 1.51 and 1.52 times of that of the 3-year, respectively. However, the abundance of amoA gene showed an opposite trend. The amoA gene copy number in the 14-year sample was 3.28 x 10(7) copies x g(-1) soil, which was only 45.7% of that of the 3-year. These results illustrated that the ecological adaptation mechanisms of the different functional microorganisms involved in nitrogen cycling had significant differences in the facility vegetable soils, and provided a base for further researches on exploring and explaining the characteristics and adaptation mechanisms of microorganisms in greenhouse soil.

[Concentration and speciation of arsenic in greenhouse vegetable soil in Shouguang County of Shandong Province].

A sampling survey was conducted in the typical areas in Shouguang County of Shandong Province to study the characteristics of arsenic (As) concentration and speciation in greenhouse vegetable soil. The total As concentration in the surface (0-20 cm) and subsurface (20-40 cm) soil was averagely 8.27 and 7.93 mg x kg(-1), being 19% and 23% higher than that of the control (open field soil), and the soluble As (AE-As) concentration was 0.13 and 0.06 mg x kg(-1), 63% and 200% higher than that of the control, respectively. The ratio of residual As (O-As) to total arsenic reached more than 63.0%, and the concentrations of different As speciation decreased in the order of O-As > iron-bound As (Fe-As) > calcium bound As (Ca-As) > aluminum bound As (AlAs) > AE-As. With the increasing planting years, the AE-As concentration enhanced significantly, and the Al-As concentration also increased to some degree. After 15 years planting, the AE-As concentration in surface and subsurface soil increased by 75.0% and 150.0%, and Al-As concentration increased by 51.6% and 190.4%, respectively, while the concentrations of Fe-As and Ca-As all decreased to some degree.

[Effects of exogenous dimethylarsinic acid on Brassica campestris growth and soil arsenic bioavailability].

A pot experiment was conducted to study the effects of exogenous dimethylarsinic acid (DMA) on the growth of Brassica campestris and the bioavailability of soil arsenic (As). With the increasing concentration of applied DMA, the emergence rate and biomass of B. campestris increased at low concentration DMA, but decreased at high concentration DMA. When the DMA concentration reached 90 mg x kg(-1), the emergence rate and biomass of B. campestris in the second cropping decreased by 9.5% and 57.0%, respectively, compared with those in the control, indicating that exogenous DMA had longer-term effects on the growth of B. campestris. The soil available As and the As uptake by B. campestris all increased with increasing concentration of exogenous DMA, and there existed significant correlations among them. After applied into soil, the exogenous DMA demethylated, with As(V) as the main product and lesser amount of As (III), and the concentrations of soil As(V) and As(III) increased with increasing application rate of exogenous DMA.